Ralph Stuart, CIH Laboratory Ventilation Specialist

Dept. of Environmental Health and Safety rstuart@cornell.edu

March, 2012

Laboratory Ventilation: Rethinking the Traditions

What is Environmental Health and Safety?

Environmental Health and Safety

ComplianceSafety

Education Lab Productivity

• Labs are workplaces where people do unusual things with hazardous materials

• Generic strategies are used to protect the workers and the work:

1. Hazard replacement or downsizing 2. Facility design and operation 3. Worker training and oversight 4. Personal protective equipment and emergency

response plans • This approach maximizes the ability of the

facility to host a variety of work.

What is a Lab?

The challenge is balancing contrasting priorities for facilities:

• The flexibility required by laboratory work

• The definition and time needed by building designers and operators to plan and provide a safe facility

“Safe” can compete with sustainability. For example, a simple approach to this challenge is to throw lots of air at the problem.

Science and Safety

How Does Sustainability Fit Into This?

• Sustainability involves environmental aspects which go “beyond compliance”

• Health and safety goes beyond compliance as well. • Laboratory Ventilation is one of the bridge issues

between EHS and sustainability • The increase and intensification of laboratory

research over the last two decades has led to health and safety issues that go beyond traditional lab safety models (chemical, biological and radiation hazards as distinct concerns)

What is Lab Ventilation for?

The goal of lab ventilation is to control: 1.Space temperature 2.Fire hazards 3.Odors 4.Toxicity 5.Incoming dust levels (possibly) 6.Humidity (possibly) - when dilution is the solution to pollution

The first method of ventilating labs was opening windows.

Four Reasons Chemistry Shouldn’t Smell

• It indicates a poor atom economy (a key principle of Green Chemistry)

• Fugitive odors can mask more serious leaks • Other people shouldn’t have to smell your work • Do you want to be part of the index population for

your chemicals?

So, Fume Hoods: The Sustainability Concern

• In terms of heating and air conditioning energy impact, 1 fume hood = 3.5 houses

• Face velocity: what’s the right one? • The Ergonomic Challenge of Hood Work • How much protection does a hood

provide? It depends.

Fume Hoods: the EHS Concerns

Hood air flow did not or would not have helped with

the 3 lab accidents cited last fall by the US

Chemical Safety Board (dermal toxicity, large fire,

explosion)

An Example of anEHS / Sustainability Connection

• Variable air volume (VAV) hoods use electronic controls to maintain 100 fpm face velocity as the sash height changes • The controls balance supply and exhaust air to a space as the hood sash is lowered to pull less air is out of the lab • The electronics can also be connected to occupancy sensors to reduce air flow when no one is present.

• Air Quality: use 100% outside air to avoid contaminants originating in the lab

• Air Quantity: When provided by the building, measured in air changes per hour (ACH)

• At home, this is usually less than one ACH • Highly ventilated animal rooms use 15-20 ACH

• The late 20th century approach: 10-12 ACH 24/7 in all labs

Ventilation outside the Hood, Inside the Lab

• How many ACH are needed depends on what’s happening in the room and how effective the ventilation is

• Ventilation need can be driven by: • Chemicals and other hazards • Local exhaust requirements • Temperature (solar and plug load)

The 21st Century Approach

• For protection from chemicals, we have been sorting Cornell labs into Control Bands • We start with a standard minimum of 8 ACH when

the lab is unoccupied and 4 ACH when unoccupied to control chemical concentrations

• We’ve been identifying many labs where we expect 6 ACH and 3 ACH to be adequate to control chemical hazards.

• There are special cases outside these generic categories (e.g. animal areas, BSL rooms)

• However, often exhaust requirements or temperature management trumps chemical issues

Planning Lab Ventilation for Safety and Sustainability

Key Questions that have arisen

1.What safety value do we get out of the air we supply to labs?

2.What’s difference between 8 and 6 ACH in terms of controlling chemical concentrations?

3.Can we go lower than 6 air changes per hour?

Finding Some Answers

• We use carbon dioxide to measure and compare chemical concentration decay patterns within a laboratory

Key Results

• Major sources (that fill the room) – Horizontal variation depends on furniture configuration – Measured ACH is lower than building supplied ACH

• Minor sources (that don’t fill the room) – More descriptive of lab events – Measured ACH is higher than building supplied ACH

• The concentration decay is logarithmic, so the time factor is better described as a “half-life” (= ln(2)/ACH)

Concentration half life and ACH

8 ACH = half life of 5 minutes 6 ACH = half life of 7 minutes 4 ACH = half life of 10 minutes 2 ACH = half life of 21 minutes

EHS Interpretations

• To control chemical concentrations, lab air must be single pass air. • In lab situations, the difference in effectiveness between 6 and

8 ACH is small; the size of the room is as important as the ventilation system in providing safety

• Chemical housekeeping, flammable storage cabinets, and local exhaust are the best ways to control chemical “hotspots” in the lab, for both safety and sustainability

• What about fume hoods? • Hoods are popular because they address the first two points

when they are used. • However, hoods often aren’t used (correctly) because they are

a significant ergonomics challenge. • It’s not clear that they need as much air as they currently use.

Lab Energy Conservation Opportunities

• Identify hoods that can be decommissioned • Reduce face velocity on hoods that can maintain

containment • Set default ACH to 6 when chemical processes

allow • Educate occupants about the role of lab ventilation

in a safe laboratory and why more isn’t better • Start reducing electricity plug load to lower

ventilation requirements (Labs-21)

http://www.nature.com/news/2011/110518/full/473263a.html [In the aftermath of the earthquake], the University of Tokyo… cut peak power usage by 30–40% by turning off lights and air-conditioning, shutting down extra lifts, and running energy-intensive experiments at night. Researchers at the university say that their low-energy lives are inconvenient, but largely manageable... "The electricity shortage made us realize that we can indeed save energy easily by 10%, but that 30% cuts will impact productivity in the longer term”, one said.

Today’s Lab Greening Moment?

Questions?